Quantitation of hepatitis C virus (HCV) RNA in serum has been
used to predict and monitor the efficacy of interferon therapy in
chronic HCV infection. We prospectively studied the fluctuation of
viremia by a longitudinal follow-up of HCV RNA levels for 2 months
in six untreated patients. Spontaneous fluctuations of HCV RNA
ranged from 2.8- to 5.7-fold with branched DNA assay and from 2.9-
to 5.6-fold with Monitor. These large spontaneous fluctuations (up
to 0.75 log), observed daily, weekly, and monthly, raise doubt
about the clinical value of a single assessment of pretherapeutic
viremia.